GAIN AND DIFFERENTIAL GAIN OF SINGLE-LAYER INAS GAAS QUANTUM-DOT INJECTION-LASERS/

We present gain measurements and calculations for InAs/GaAs quantum do t injection lasers. Measurements of the modal gain and estimation of t he confinement factor by transmission electron microscopy yield an exc eptionally large material gain of 6.8(+/-1)x10(4) cm(-1) at 80 A cm(-2 ) Calculations including realistic quantum dot energy levels, dot size fluctuation, nonthermal coupling of carriers in different dots, and b and filling effects corroborate this result. A large maximum different ial gain of 2x10(-12) cm(2) at 20 A cm(-2) is found. The width of the gain spectrum is determined by participation of excited quantum dot st ates. We record a low transparency current density of 20 A cm(-2). All experiments are carried out at liquid nitrogen temperature. (C) 1996 American Institute of Physics.